Method of forming a gridlike structure



Feb. 11, 1941. M. LACHMAN METHOD OF FORMING A GRIDLIKE STRUCTURE FiledSept. 15, 1936 2 Sheets-Sheet 1 Feb. 11, 1941.

M.. LACHMAN 2,231,450

METHOD OF FORMING A GRIDLIKE STRUCTURE Filed Sept. 15, 1936 2Sheets-Sheet 2 on 7" 1M 9 ATTORN EYS Patented Feb. 11, 1941 2,231,450

UNITED STATES PATENT OFFICE METHOD OF FORMING A GRIDLIKE STRUCTUREMaurice Lachman, New York, N. Y., assignor to L. T. Corporation, JerseyCity, N. J., a corporation of New Jersey Application September 15, 1936,Serial No. 100,837

2 Claims. (01. 219-10) This invention relates to grills or gratingsapalso producing a structure in which no waste of plicable for use asrefrigerator shelvings or trays metal occurs during the weldingoperation. and comprising a plurality of spaced metallic To the aboveends, the invention consists in the longitudinal members united to aplurality of novel process of making a gridlike structure as spacedmetallic transverse or crossing members, hereinafter more particularlydescribed and then 5 preferably by the well-known electrical resistancespecified in the claims. method wherein pressure is applied to thecross- In the accompanying drawings illustrating a ing or intersectingmembers by suitable dies that practical embodiment of the gridliliestructure also furnish the means of applying heating curproducedaccording to the method of the rent to the work. The intersectingmembers at inven ion 10 their points of intersection are thus united ina Fig. l is a plan View of a portion of the grill homogeneous orautogenous electric weld to pro- 1 g a Other gridlike Structureembodying duce a composite, integral structure. It will be theinvention.

understood from the subjoined description that 2 iS a d V Of theinvention in its application isnot to be limited Fig. 3 is an nla ed pan w f w f h 15 in its use to refrigerator trays, but its applicai e ecmemberstion may be readily extended to other fields such, F g- 4 S abotto V ew O F ior instance, as gratings for sidewalks, etc. g- 518 an dV ew of The principal object of the invention is the 6 is a S eelevation (partly in section) of production of a grill r grating oanalogous afragmentary portion of two of the crossing mem- 20 grid-likestructure of the general character herehere assembled for union at their{mints of intertofore described which shall possess extreme i n by th ltri l r si n e W n rigidity and strength while at the same time bep ingof ease and simplicity of manufacture at 7 shows the p i i f a r inmemrelatively small expense. bers after the welding or union'has beeneffected 25 A further object of the invention is the pro-' y theaforesaid P ce duction of a grill or grating of the character 8 is a pan v w f a s t n f a r ll or described having an externally smoothuniform grating Showing a m d fi Dn Of t e invention surface on bothfaces thereof, that is, a grill or in which the in mem rs mpri erecgrating in which both faces thereof are subtangularly-shaped barsinstead of rounded wires 30 stantial duplicates or unt r t i configuraorrods as in the preferred form of the invention.

tion and appearance to permit the device to be 9 is an d V ew f F g- 3.readily reversed should occasion arise while still 10 is a p V Of afragmentary P n retaining its desirable mechanical, structural and ofthe l t d structu sh in w n y of ornamental f at s the intersecting orcrossing members. 3

Still a further object of the invention is the Fig; 11 is a horizontalsection on the line li-l| production of a grill or grating comprisinginterof Fi secting or crossing metallic members electrically g- 12 S S wo t Crossing members in welded together to form a composite and integralsection and assembled for union by the electrical open structure inwhich the electric Welds uniting resistance W l in p and, 40

the members together occupy a common pl ne Fig. 13 is a similar view butshowing said crosswith the plane of the united members on both s membersaf r h w l in per ion h s faces of the structure, that is, the electricwelds be n ected.

occupy a common plane with the plane of the Referring in detail to theseveral figures of the crossing members themselves whereby the grill ordrawin 45 grating will be substantially smooth on both faces. Thetransverse members of the grill or gratin A further object of theinvention is the proare indicated at and comprise metallic rods ductionof a grill or grating or analogous strucor wires which are pre e a yspaced ap r q ture of the character described in which the distantly asillustrated. The metallic longicrossing or intersecting members areunited totudinal members, which are indicated at 2, are 50 gethel' insuch manner as to produce a finished p f r y f he same size or diameters said product in which no burr has been thrown out transverse members Iand are also equidistantly during the electric welding process inuniting spaced apart, as shown, and are united to said such memberstogether thereby obviating any transverse members in the manner about tobe unsightly deformation of the united members and described whereby anopenwork, integral structure is produced which is peculiarly adapted inits application for use as screen shelving and grills, etc. for refigerators.

In constructing the grill or grating heretofore described thelongitudinal metallic members 2 are assembled in spaced relation to eachother and the transverse metallic members are then placed thereon inspaced relation (see Fig. 6) or vice versa and preferably atright-angles with respect thereto, or the members may be directeddiagonally of each other or may extend in other directions and still bewithin the scope of the invention. At their places of intersection orcrossing one set of the members is united to the other as at 3, to formautogenous or homogeneous electrically welded joints so that the jointitself shall be 531811 with the common plane in which both crossingmembers are situated.

To effect the autogenous or integral union of the members at thecrossing thereof or at the place of their intersection, I employ theelectrical resistance and pressure method and apply heating current andpressure at the point of their crossing by means of the weldingelectrodes or dies =l 5 and until the members i and 2 are brought into acommon plane with one another and with the general plane occupied bythem in the finished structure as indicated in Figs. 1. 2, 3, i, 5, '7.The pressure of the dies is continued until their movement toward eachother is further prevented by the unheated and unsoftened portion of themembers as shown in Fig. '7.

In the welding operation described it is extremely important thatwelding current of suiiicient strength for fusing the members at theirplaces of crossing be not maintained longer than a predetermined periodof time to prevent the fusing or melting of the intersecting members toa degree of plasticity which might result in bisecting one or both ofthe members. Accord ngly, in the process, a quick and heavy heatingcurrent is first applied to the members at the place of their crossing,the intensity or volume of which is decreased after a predeterminedinterval of time and the process is then continued with a slow heatingto preserve the plastic condition of the intersecting parts, swagingpressure being applied by the electrodes or dies to flatten and pressout the ma erial in the direction of the longitudinal axis of eachintersecting member. A homogeneous and autogenous welded joint ofmaximum strength is thus produced and one in which no burr appears or isthrown out and in which no waste metal obtains or is present.

As is obvious, the pressure of the di s at the time of the completing ofthe welding operation, will result in a slight flattening of theintersecting members at their points of intersection and in thedirection of their longitudinal axes but the softened or welded portionof the metal in said members will merge in the undeformed portionthereof and will lie within the general plane of the crossed members onboth sides or faces of the structure whereby neither surface of thefinished structure will offer obstruction to the movement of objectsacross its face. This feature, of course, is advantageous when thestructure is employed as a tray or shelving for refrigerators. When itis to be so used, obviously, a frame of any material may be fastened orconnected to the free ends of he members i and 2 in any desirablemanner.

In the modification illustrated in Figs. through 13 inclusive I preferto employ fiat rectangular bars or plates instead of the rounded rods orwires as in the preferred form of the invention. In said modification 6indicates the transverse members and I the longitudinal members of thestructure which are united together by homogeneous and autogenous jointsin the same manner as heretofore described in the prefe red form of theinvention. In this case the upper and lower welding and pressure dies orelectrodes are indicated by the reference numerals 8 and 9 respectively.

I find it desirable in some cases to provide the grill or grating at theplaces of intersection between the transverse and longitudinal memberswith an ornamental button, indicated at ill, having a depressed portioncentrally thereof as illustrated. When the structure is used as a shelfor tray for refrigerators, the button if! is provided for the purpose ofornamentation only and to enhance the appearance of the structure, whreas if it is used, for instance, as a grating for sidewalks or foranalogous uses the button may conveniently provide a non-skid tread.When employing the button a specially prepared upper electrode or die Plis used and is provided with a depending annular portion H. A suplemental rounded or annular metallic member [8 is also employed and isinterposed intermediate the portion it of the upper weldin die 8 and thetransverse member 6 at the point of its intersection with thelongitudinal member l. When the dies 3 and ,9 are brought into weldingposition and pressure is app ied thereagainst the member 13 thereuponbecomes welded to the structure and becomes a composite and integralpart thereof, the depression centrally of the member it being formed bythe annular portion H on the upper welding die 8 as will be manifest.

Various modifications may be resorted to without departing from thespirit of the invention as set forth in the appended claims.

The invention claimed is:

1. The method of forming a grid structure by uniting metallic memberstogether consisting in bringing into surface contact two crossingmembers of substantially uniform cross section and of a cross section attheir crossing points substantially equal to the original cross section,both of said members being of the same cross section, applying pressureand a heavy heating electric current at the point of intersection ofsaid members for a predetermined period of time to fuse, coalesce andcompact the metal of said members to reduce their combined cross-sectionunder the applied pressure to an extent approximately equal to theoriginal cross section of one of the members at the crossing point, andthen reducing the strength of the current to continue the process withslow heating and continued pressure to further coalesce and compact themetal to produce a structure wherein the portions of metal of themembers at the point of intersection are homo geneously and integrallycombined whereby the outer surfaces of the members occupy the samecommon plane on each face of said structure.

2. The method of forming a metallic structure comprising two sets ofmeta lic members circular in cross section and of substantially equalcrosssectional area consisting in bringing unreduced portions of themembers in crossed relation and into surface contact, subjecting saidmembers at their points of contact to welding heat to fuse the metalthereof at said points and simultaneously subjecting the members topressure to permit the molten metal to spread laterally at the jointsand longitudinally of the me bers to form flattened areas and thenreducing the strength of the current to continue the process with slowheating and continued pressure to homogeneously and integrally combinethe metal of the members and produce a structure in which like surfacesof said flattened areas are substantially flush with each other on eachface of said structure and one in which like surfaces of the members lieon each side of the completed structure within two planes spaced apart adistance substantially equal to the thickness of one of the members.

MAURICE LACHMAN.

